zhisheng17/flink-learning · error · SqlParserException

Unsupported command '{}'

Error message

Unsupported command '{}'

What it means

SqlCommandParser.parseLine throws SqlParserException when a semicolon-terminated statement cannot be parsed into a known SqlCommandCall. The parser matches the first keyword against a registry of supported SQL commands (INSERT INTO, CREATE TABLE, etc.); anything unrecognized — including empty statements or stray semicolons — fails. This is a fail-fast guard so invalid scripts abort before reaching the planner.

Source

Thrown at flink-learning-sql/flink-learning-sql-client/src/main/java/com/zhisheng/sql/cli/SqlCommandParser.java:28

public final class SqlCommandParser {

    private SqlCommandParser() {
    }

    public static List<SqlCommandCall> parse(List<String> lines) {
        List<SqlCommandCall> calls = new ArrayList<>();
        StringBuilder stmt = new StringBuilder();
        for (String line : lines) {
            if (line.trim().isEmpty() || line.startsWith("--")) {
                continue;
            }
            stmt.append("\n").append(line);
            if (line.trim().endsWith(";")) {
                Optional<SqlCommandCall> optionalCall = parse(stmt.toString());
                if (optionalCall.isPresent()) {
                    calls.add(optionalCall.get());
                } else {
                    throw new SqlParserException("Unsupported command '" + stmt.toString() + "'");
                }
                stmt.setLength(0);
            }
        }
        return calls;
    }

    public static Optional<SqlCommandCall> parse(String stmt) {
        stmt = stmt.trim();
        if (stmt.endsWith(";")) {
            stmt = stmt.substring(0, stmt.length() - 1).trim();
        }

        for (SqlCommand cmd : SqlCommand.values()) {
            final Matcher matcher = cmd.pattern.matcher(stmt);
            if (matcher.matches()) {
                final String[] groups = new String[matcher.groupCount()];
                for (int i = 0; i < groups.length; i++) {

View on GitHub (pinned to d731cee761)

Solutions

  1. Fix the SQL statement to use a command registered in SqlCommand parser lookup (INSERT INTO, CREATE TABLE, CREATE FUNCTION, etc.)
  2. If you intended a SELECT query, wrap it as INSERT INTO <sink> SELECT ... or use EXPLAIN if supported
  3. Check for typos and stray semicolons in the statement before the failing ';'
  4. Extend the SqlCommand enum/parser registry to support the missing command type if it is a valid Flink SQL statement

Example fix

// before
SELECT id, name FROM users;
// after
INSERT INTO print_sink SELECT id, name FROM users;
Defensive patterns

Strategy: validation

Validate before calling

String trimmed = stmt.trim();
if (trimmed.isEmpty() || !trimmed.matches("(?i)(INSERT\\s+INTO|CREATE\\s+(TABLE|FUNCTION)|EXPLAIN)\\b.*")) {
    throw new IllegalArgumentException("Statement not supported by parser: " + stmt);
}

Try / catch

try {
    Optional<SqlCommandCall> call = parse(stmt);
    call.ifPresent(calls::add);
} catch (SqlParserException e) {
    LOG.error("Skipping unsupported statement: {}", stmt, e);
}

Prevention

When it happens

Trigger: Calling SqlCommandParser.parse (via parseLine) with a statement whose leading keyword is not a registered SqlCommand, e.g. a bare 'SELECT 1;' (no INSERT/EXPLAIN wrapper), a typo like 'CREAT TABLE ...;', or an empty/whitespace-only statement ending with ';'.

Common situations: Running a SQL script file through the sql-client that contains plain SELECT queries the parser doesn't support, comments or SET syntax mis-handled by a custom client, or copy-pasted SQL with typos in DDL/DML keywords.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of zhisheng17/flink-learning@d731cee761 (2026-09-06). Data as JSON: /api/errors/baeab4253a311b48. Report an issue: GitHub.